| Abstract: | The helix–coil transition of poly-N5-(3-hydroxypropyl)-L -glutamine (PHPLG) has been studied in methanol–water by CD and cmr spectroscopy. For polydisperse PHPLG, two separate peaks arising from residues in helical and random-coil conformations are observed during the transition for both main-chain carbons. These results are discussed and compared to those observed in the case of a polymer sample obtained by racemization of PHPLG in 0.1 M NaOH and of PHPLG samples of controlled molecular weight and dispersity. The dominant influence of the molecular-weight heterogeneity on the double-peak phenomenon has been verified. The linewidths and chemical shift of the 13C resonances are discussed in terms of side-chain–main-chain interactions and side-chain solvation. |
